From c5454038d5d8795ddee95bee8085972530c08f3f Mon Sep 17 00:00:00 2001
From: Ben Brady <benbrady04.bb@gmail.com>
Date: Sat, 9 Aug 2025 02:55:00 +0100
Subject: [PATCH] =?UTF-8?q?=F0=9F=94=A8=20tweaked=20encoder=20primative=20?=
 =?UTF-8?q?key=20skip=20to=20disallow=20subclasses?=
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---
 fastapi/encoders.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fastapi/encoders.py b/fastapi/encoders.py
index b43d372d2..41c589d49 100644
--- a/fastapi/encoders.py
+++ b/fastapi/encoders.py
@@ -375,7 +375,9 @@ def encode_dict(
         if key not in allowed_keys:
             continue
 
-        if isinstance(key, primitive_types):
+        # use type() in, instead of isinstance
+        # we don't want to allow subclasses, they should be encoded still
+        if type(key) in primitive_types:
             encoded_key = key
         else:
             encoded_key = encode_value(